Effect of hazelnut protein oxidation on O/W emulsion stability, interfacial properties and lipid oxidation based on hazelnut protein oxidation

Abstract

The objective of this study was to examine the impact of hazelnut proteins with varying levels of oxidation (0, 45, 90, 135, 180, and 225 d of storage) on the stability of O/W emulsions. The results demonstrated that hazelnut proteins with varying degrees of oxidation exhibited distinct effects on the stability of O/W emulsions. Mild and moderate oxidation resulted in an increase in the absolute ζ-potential, surface hydrophobicity, endogenous fluorescence intensity, centrifugal stability, emulsification index, adsorbed protein content, and viscosity of the emulsions, it caused a decrease in particle size and turbidity, ultimately leading to an improvement in the physical stability of hazelnut protein emulsions. Electrophoresis results demonstrate that proteins with moderate oxidation exhibit increased flexibility, which contributes to the development of a more compact interfacial structure and improved stability of emulsions. The decrease in viscosity as the shear rate increases suggests that hazelnut protein emulsions are characteristic of shear-thinning systems. Additionally, frequency scans reveal that all emulsions display an improved elastic structure in both the mid-and high-frequency ranges. Oil oxidation is an unavoidable process that occurs over extended periods of storage. However, emulsions containing a moderate level of protein oxidation exhibit reduced levels of oil oxidation products in comparison to other emulsions. This characteristic contributes to the stabilization of oil-in-water (O/W) emulsions. In conclusion, hazelnut proteins that have undergone moderate oxidation exhibit beneficial effects on emulsion stability, interfacial properties, and lipid oxidation.